Re-use your bottles

'Empty vessels make most noise' is a phrase I remember from childhood, along with 'Use your initiative.' I seem to remember that if I did use my initiative the words 'You thought? You THOUGHT?!' came my way soon after.

But today's post is not about my happy reminiscences but about sound - the science of sound. By the end of the seasonal festivities, if indeed you haven't already, you should find yourself with easy access to numerous empty bottles of varying sizes. You may already be able to play a bottle by blowing across the top, aiming a jet of air at the opposite section of the rim. If not, perhaps you can persuade someone to teach you.

Now if you sound a plastic bottle in this way, and then a glass bottle of the same capacity, will the pitch be the same?

Are bottles of greater volume pitched higher or lower than those of smaller volume?

Do all glass bottles of the same capacity have the same pitch? Will shape or thickness of glass make a difference?

Never again be a wallflower at a party! The cool folk may steer a wide berth but you're never alone with a bottle.

Twang on a can

Here, as unwisely promised yesterday, is a clip of me twanging the ring-pull of an aluminium fizzy drink can whilst simultaneously filling it with water. What do you think happens to the pitch of the note?

My own, subjective and non-scientific, opinion is that the pitch stays the same. The note seems to get higher because the upper harmonic partials are increasingly favoured as the can fills. If I were to blow the can like a flute then I would hear the air inside vibrating. Less volume of air, as the water replaces it, means a gradual rise in pitch. When I twang the can it is the can I hear resonating. The water dampens (no pun intended - 'deadens' might be a better word) the sound of the lower partials.

Today I went for a long walk by the sea so no sonic experiments. But tomorrow I shall continue to explore the seasonal debris and make some more rubbish instruments. If you would like to join in then hang on to all sizes of bottles, both glass and plastic, tin cans of various types, wrapping paper and anything else you think might produce a noise.